Extremal Values of the Chromatic Number for a Given Degree Sequence

International audienceFor a degree sequence d : d 1 ≥ · · · ≥ d n , we consider the smallest chromatic number χ min (d) and the largest chromatic number χ max (d) among all graphs with degree sequence d. We show that if d n ≥ 1, then χ min (d) ≤ max 3, d 1 − n+1 4d 1 + 4 , and, if n + 1 4 − 1 2 > d 1 ≥ d n ≥ 1, then χ max (d) = max i∈[n] min {i, d i + 1}. For a given degree sequence d with bounded entries, we show that χ min (d), χ max (d), and also the smallest independence number α min (d) among all graphs with degree sequence d, can be determined in polynomial time

Extremal Values of the Chromatic Number for a Given Degree Sequence

International audienceFor a degree sequence d : d 1 ≥ · · · ≥ d n , we consider the smallest chromatic number χ min (d) and the largest chromatic number χ max (d) among all graphs with degree sequence d. We show that if d n ≥ 1, then χ min (d) ≤ max 3, d 1 − n+1 4d 1 + 4 , and, if n + 1 4 − 1 2 > d 1 ≥ d n ≥ 1, then χ max (d) = max i∈[n] min {i, d i + 1}. For a given degree sequence d with bounded entries, we show that χ min (d), χ max (d), and also the smallest independence number α min (d) among all graphs with degree sequence d, can be determined in polynomial time